An AgX emulsion comprising tabular grains having a {100} plane as a main plane and an aspect ratio of 1.5 to 7.0 which has been prepared via at least nucleation and ripening procedures is disclosed in U.S. Pat. No. 4,063,951. In the preparation of such an AgX emulsion, however, it is essential that NH.sub.3 be present in the system in an amount of 0.1 to 1.0 mol/l during the ripening procedure. If the ripening procedure is effected with NH.sub.3 present in the system, the resulting tabular grains have a low aspect ratio but have a disadvantage that they have a high fog density.
On the other hand, U.S. Pat. No. 4,386,156 discloses an AgX emulsion comprising tabular grains having an aspect ratio as high as 8 or more which has been ripened with no AgX solvent present in the system. However, tabular grains having an average aspect ratio of 8 or more are disadvantageous in that when incorporated in a photographic light-sensitive material, the resulting photographic light-sensitive material exhibits pressure characteristics poor enough to cause pressure fog. Accordingly, it has been desired to develop an AgX emulsion comprising tabular grains having an aspect ratio of less than 8 which is insusceptible to pressure fog and exhibits a low fog density. However, such an AgX emulsion is unknown. Such tabular grains are characterized by a higher color-sensitizability than other AgX grains.
Since all the grains disclosed in the above cited patents have been prepared via nucleation and ripening procedures only, there occurs another problem in that the resulting yield of AgX emulsion is too low and a free or variable control of the grain diameter can not be obtained.